The issue with Firefox/Opera, and most Mozilla engine based browsers, is a known issue. Mozilla recently changed the way they handle form data and as a consequence broke the web pages on those browsers. This issue has been fixed in revision 3.0 of the firmware.

The Linux ping is a different size than Windows (Windows is 32 bytes). If you change the Linux ping size to 32 bytes, the GC-100 should respond to the ping.

Anyway I need to set it up properly again soon and I was wondering: can the firmware be upgraded, if so, where to obtain and how to apply it. This does not seem to be adressen in the FAQ or anywhere else I looked.